Method and system for narrow  grove welding using laser and hot-wire system

ABSTRACT

A system and method for narrow groove welding is provided. The system includes at least one laser emitting a laser beam to heat at least one of a first workpiece and a second workpiece to create at least one molten puddle. The system also includes at least one wire feeder feeding at least one wire to the at least one molten puddle. An edge of the first workpiece and an edge of the second workpiece are configured such that an alignment of the workpieces forms a first groove and a second groove. The first groove and the second groove are formed on opposite sides of the workpieces. For each groove, its depth is 50% to 75% of a thickness of the first workpiece or the second workpiece, a gap width at a surface of the workpieces is 1.5 to 2 times a diameter of the at least one wire, and a sidewall angle is a range of 0.5 to 10 degrees with respect to a centerline of the respective groove.

PRIORITY

The present application claims priority to U.S. Provisional PatentApplication No. 61/679,492 filed Aug. 3, 2012, which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

Certain embodiments relate to narrow groove welding and joiningapplications. More particularly, certain embodiments relate to the useof a laser and filler wire in a system and method for narrow groovewelding and joining applications.

BACKGROUND

The traditional hot filler wire method of welding (e.g., a gas-tungstenarc welding (GTAW) hot filler wire method) provides increased depositionrates and welding speeds over that of traditional arc welding alone. Thefiller wire, which leads a torch, is resistance-heated by a separatepower supply. The wire is fed through a contact tube toward a workpieceand extends beyond the tube. The extension is resistance-heated suchthat the extension approaches or reaches the melting point and contactsthe weld puddle. A tungsten electrode may be used to heat and melt theworkpiece to form the weld puddle. The power supply provides a largeportion of the energy needed to resistance-melt the filler wire. In somecases, the wire feed may slip or falter and the current in the wire maycause an arc to occur between the tip of the wire and the workpiece. Theextra heat of such an arc may cause burnthrough and spatter.

In addition, it can be difficult to weld the bottom of the joint whenarc welding deep joints (greater than 1 inch in depth). This is becauseit is difficult to effectively deliver shielding gas into such a deepgroove and the narrow walls of the groove can cause interference withthe stability of a welding arc. Further, because the workpiece istypically a ferrous material the walls of the joint can interfere,magnetically, with the welding arc. Because of this, when using typicalarc welding procedures the width of the groove needs to be sufficientlywide so that the arc remains stable. However, the wider the groove, themore filler metal is needed to complete the weld.

Further limitations and disadvantages of conventional, traditional, andproposed approaches will become apparent to one of skill in the art,through comparison of such approaches with embodiments of the presentinvention as set forth in the remainder of the present application withreference to the drawings.

SUMMARY

Embodiments of the present invention comprise using a laser and fillerwire in a system and method for narrow groove welding and joiningapplications. The system includes at least one laser emitting a laserbeam to heat at least one of a first workpiece and a second workpiece tocreate at least one molten puddle. The system also includes at least onewire feeder feeding at least one wire to the at least one molten puddle.An edge of the first workpiece and an edge of the second workpiece areconfigured such that an alignment of the workpieces forms a first grooveand a second groove. The first groove and the second groove are formedon opposite sides of the workpieces. For each groove, its depth is 50%to 75% of a thickness of the first workpiece or the second workpiece, agap width at a surface of the workpieces is 1.5 to 2 times a diameter ofthe at least one wire, and a sidewall angle is a range of 0.5 to 10degrees with respect to a centerline of the respective groove.

The method includes aligning an edge of a first workpiece to an edge ofa second workpiece and heating at least one of the first workpiece andthe second workpiece to create at least one molten puddle. The methodalso includes feeding at least one wire to said at least one moltenpuddle. The edge of the first workpiece and the edge of the secondworkpiece are configured such that the aligning forms a first groove anda second groove, which are formed on opposite sides of the workpieces.

These and other features of the claimed invention, as well as details ofillustrated embodiments thereof, will be more fully understood from thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the invention will be more apparent bydescribing in detail exemplary embodiments of the invention withreference to the accompanying drawings, in which:

FIG. 1 illustrates a functional schematic block diagram of an exemplaryembodiment of a combination filler wire feeder and energy source systemfor narrow groove welding and joining applications;

FIG. 2 illustrates an exemplary embodiment of the grooves G, G′ of thesystem in FIG. 1;

FIG. 3 illustrates an exemplary embodiment of a joint between workpiecesthat is consistent with embodiments of the present invention; and

FIGS. 4A to 4C illustrate exemplary embodiments of a joint betweenworkpieces that are consistent with other exemplary embodiments of thepresent invention.

DETAILED DESCRIPTION

Exemplary embodiments of the invention will now be described below byreference to the attached Figures. The described exemplary embodimentsare intended to assist the understanding of the invention, and are notintended to limit the scope of the invention in any way. Like referencenumerals refer to like elements throughout.

It is known that welding/joining operations typically join multipleworkpieces together in a welding operation where a filler metal iscombined with at least some of the workpiece metal to form a joint.Because of the desire to increase production throughput in weldingoperations, there is a constant need for faster welding operations,which do not result in welds which have a substandard quality.Furthermore, there is a need to provide systems that can weld quicklyunder adverse environmental conditions, such as in remote work sites. Asdescribed below, exemplary embodiments of the present invention providesignificant advantages over existing welding technologies. Suchadvantages include, but are not limited to, reduced use of filler wire,reduced fabrication time, reduced total heat input resulting in lowdistortion of the workpiece, very high welding travel speeds, very lowspatter rates, welding with the absence of shielding, welding plated orcoated materials at high speeds with little or no spatter, and weldingcomplex materials at high speeds.

Furthermore, many types of welding and joining applications use standardbutt or v-notch groove joints to join the work pieces. However, thesejoint types can require great care when aligning the workpieces, and ifthey are misaligned the joint can be compromised or may need to bere-worked. However, embodiments of the present invention allow for theweld joint shape to be formed such that alignment can be optimized andmade quicker, with less chance for misalignment.

FIG. 1 illustrates a functional schematic block diagram of an exemplaryembodiment of a combination filler wire feeder and energy source system100 for performing joining/welding applications. The system 100 includesa laser subsystem 130/120 capable of focusing a laser beam 110 onto oneside of workpieces 115A and 115B to form a weld puddle 145. System 100also includes a laser subsystem 230/220 capable of focusing a laser beam210 onto the other side of workpieces 115A and 115B to form a weldpuddle 245. The laser subsystems are a high intensity energy sources andcan be any type of high energy laser source, including but not limitedto carbon dioxide, Nd:YAG, Yb-disk, YB-fiber, fiber delivered or directdiode laser systems. Further, even white light or quartz laser typesystems can be used if they have sufficient energy. For example, a highintensity energy source can provide at least 500 W/cm².

It should be noted that the high intensity energy sources, such as thelaser devices 120/220 discussed herein, should be of a type havingsufficient power to provide the necessary energy density for the desiredwelding operation. That is, the laser devices 120/220 should have apower sufficient to create and maintain a stable weld puddle throughoutthe welding process, and also reach the desired weld penetration.Exemplary lasers should have power capabilities in the range of 1 to 20kW, and may have a power capability in the range of 5 to 20 kW. Higherpower lasers can be utilized, but can become very costly.

Each laser subsystem includes a laser devices 120 or 220 and laser powersupply 130 or 230. The laser devices are operatively connected to theirrespective power supplies. The laser power supplies 130/230 providepower to operate the respective laser devices 120/220. The laser devices120/220 allow for precise control of the size and depth of therespective weld puddles 145/245 as the laser beams 110/220 can befocused/de-focused easily or have the beam intensities changed veryeasily. Because of these abilities, the heat distribution on theworkpieces 115A/115B can be precisely controlled. This control allowsfor the creation of the very narrow weld puddles that are important forthe deep groove type welding of the present invention.

The system 100 also includes filler wire feeder subsystems capable ofproviding at least one resistive filler wire to each side of theworkpieces 115A/115B. For example, wire 140 makes contact with theworkpieces 115A/115B in the vicinity of the laser beam 110, and wire 240makes contact with the other side of workpieces 115A/115B in thevicinity of the laser beam 210. Of course, it is understood that byreference to the workpieces 115A/115B herein, the weld puddles 145/245are considered part of the workpieces 115A/115B. Thus, reference tocontact with the workpieces 115A/115B includes contact with theappropriate weld puddle 145/245 or puddles. Each filler wire feedersubsystem includes a filler wire feeder 150 and 250, a contact tube 160and 260, and a wire power supply 170 and 270. During operation, thefiller wires 140/240 are resistance-heated by electrical current fromthe power supplies 170/270, respectively. The power supplies 170/270 arerespectively connected between the contact tube 160/260 and theappropriate side of workpieces 115A/115B. In accordance with anembodiment of the present invention, the power supplies 170/270 arepulsed direct current (DC) power supplies, although alternating current(AC) or other types of power supplies are possible as well. In someexemplary embodiments, the filler wires 140/240 are respectivelypreheated by power supplies 170/270 to at or near their melting points.Accordingly, the presence of the wires 140/240 in their respective weldpuddles 145/245 will not appreciably cool or solidify the puddles andthe filler wires 140/240 will be quickly consumed into the puddles.

The power supplies 170/270, filler wire feeders 150/250, and laser powersupplies 130/230 may be operatively connected to sensing and controlunit 195. The control unit 195 can control the welding operations suchas wire feed speeds, wire temperatures, and the temperatures of the weldpuddles—to name just a few. To accomplish this, the control unit 195 canreceive inputs such as the power used by power supplies 130, 230, 170,and 270, the voltage at contact tubes 160 and 260, the heating currentsthrough the filler wires 140 and 240, the desired and actualtemperatures for the filler wires 140 and 240, etc. Application Ser. No.13/212,025, titled “Method And System To Start And Use CombinationFiller Wire Feed And High Intensity Energy Source For Welding,” filedAug. 17, 2011, and incorporated by reference in its entirety, describesexemplary sensing and control units, including exemplary monitoring andcontrol algorithms, that may be incorporated in the present invention.Accordingly, for brevity, the sensing and control unit 195 will not befurther discussed. Furthermore, the above referenced applicationdiscusses the general operation and control of a hot-wire filler systemwhich can be used with embodiments of the present invention, and thosedescriptions will not be repeated herein, as the above referencedapplication is incorporated herein by reference in its entirety.

In preparation for welding, edges a and a′ of workpiece 115A and edges band b′ of workpiece 115B have been prepped such that, once theworkpieces 115A and 115B are fitted together to form joint A, the jointA will have grooves G and G′. In exemplary embodiments, grooves G and G′are relatively narrow and deep when compared to a typical welding joint.For example, in an exemplary embodiment of the present invention wherethe workpieces 115A/115B have a thickness greater than 1 inch. Thegroove depth will be dependent on the thickness of the workpiece, butcan be in the order of 50% to 75% of this thickness. Because each grooveneed only be 50% to 75% of the thickness of the workpiece, thickerworkpieces can be welded than if the groove extended the entirethickness of the workpieces. As illustrated in FIG. 2, in some exemplaryembodiments, the gap width W (at the surface of the workpiece) of eachgroove G/G′ is in the range of 1.5 to 2 times the diameter of the fillerwire 140/240 and the sidewall angle β is in the range of 0.5 to 10degrees. For grooves that are angled (e.g., see FIG. 4A), the sidewallangle β will be with respect to a centerline of the groove. Because thegrooves G and G′ are smaller than a typical groove used in a normal arcwelding process, grooves G and G′ can be welded faster and with muchless filler material than in the normal arc welding process. Inaddition, because aspects of the present invention introduce much lessheat into the welding zone, the contact tubes 160/260 can be designed tofacilitate much closer delivery to the respective weld puddles 145/245to avoid contact with the side wall. That is, as shown in FIG. 2, thecontact tubes 160/260 can be made smaller and constructed as aninsulated guide with a narrow structure. In some exemplary embodiments,a translation device or mechanism can be used to move the lasers 120/220and the wires 140/240 across the width of the weld to weld both sides ofthe weld joint at the same time.

Thus, as shown in FIG. 1, the workpieces 115A/115B have an end shape—atthe location of the weld joint—which allows them to be easily aligned.That is, each of the workpieces 115A/115B, respectively, have surfaces190A/190B which interact with each other when the workpieces 115A/115Bare joined together. These surfaces 190A/190B aid in matching theworkpieces 115A/115B together to create the desired alignment betweenthe workpieces. When the workpieces 115A/115B are joined the surfaces190A/190B extend between the gaps G and G′. Of course, the shape ororientation of the surfaces 190A/190B can be made as desired to ensure aproper alignment is achieved.

In the exemplary embodiment shown in FIG. 1, a separate wire feeder 250and laser 220 are used to simultaneously weld on each groove G/G′ ofjoint A. However, in some embodiments, a single laser/wire feed system,which welds on one groove at a time, can be used. In other embodiments,a single laser with the appropriate optics may be used instead ofseparate lasers 120/220 to simultaneously weld on each groove G/G′ ofjoint A. In the exemplary embodiments described above, out-of-positionwelding may be required on one or both side of the joint A. Techniquessuch as controlling the intensity of the laser beam, the wire feedspeed, and heating current through the wire can help minimize thesagging of the weld puddle.

The narrow grooves in the exemplary embodiments of the present inventionallow for joint designs that help make the fabrication process quicker.For example, the typical welding joint has a gap in the root pass of thejoint. Prior to welding, the two pieces have to be carefully aligned toensure that the gap is the same along the length of the workpiece. Inaddition, the pieces may have to be tack-welded in order to ensure thatthe pieces stay in alignment during the main welding process. In someembodiments of the present invention, the need to carefully align andtack-weld the pieces may be eliminated because the joint design isself-aligning. For example, the joint A in FIG. 1 is self-aligning. Theworkpieces 115A and 115B are designed such that the bottom of sides aand b and the bottom of sides a′ and b′ abut against each other when thetwo workpieces 115A/115B are fitted in preparation for welding. Thisjoining can be facilitated by surfaces 190A and 190B. Because there isno or a minimal gap between the workpieces, the time required to alignand tack-weld the workpieces may be eliminated. In exemplary embodimentsof the present invention, there is no gap between the surfaces 190A and190B such that they are flush with each other. In other embodiments,gaps can exist between these surfaces, so long as alignment can beproperly achieved. In further exemplary embodiments, an adhesive can beapplied between these surfaces.

In yet other exemplary embodiments, a spacer can be placed between thesurfaces 190A/190B to separate the workpieces 115A/115B from each other.The spacer can be of a similar material to the workpieces or can bedifferent. For example, the spacer can be of a composition or materialthat allows dissimilar metals to be joined, where workpiece 115A is adifferent metal than workpiece 115B.

Similarly, FIG. 3 illustrates other self-aligning workpieces. In FIG. 3the joint A is formed at an angle a. By forming the joint at an angle,the metallurgical bond area between the two workpieces is greater thanif the grooves were perpendicular to the surface of the workpiecebecause the grooves G and G′ are deeper. Accordingly, the weld strengthof such as joint can be greater than the traditional joint. The angle ais greater than 0 and can be up to and including 60%.

In other exemplary embodiments of the present invention, the shape ofthe weld joint and the workpieces at the joint can vary and stillprovide the self-aligning attributes described herein. For example,FIGS. 4A to 4C illustrate exemplary joint shapes that employ a narrowgroove width design that enjoy many of the benefits discussed above suchas: self-aligning, using less filler materials than the traditional weldand providing metallurgical bond areas that are greater than thetraditional weld—to name just a few. As an example, the joint in FIG. 4Auses angled gaps G and G′ as shown, and the gaps G/G′ have a depth thatextend beyond the surfaces 190A and 190B. Thus, similar to FIG. 3 thedepth of the gaps G and G′ provide for additional surface area beingjoined. In exemplary embodiments of the present invention, the depths ofthe respective gaps do not extend beyond 75% of the thickness of theworkpieces, regardless of the relative location of the surfaces 190A and190B to the bottom of the gaps G and G′. Of course, in other exemplaryembodiments, the gaps G and G′ can be angled in opposite directions, asopposed to being angled similarly as shown in FIG. 4A.

Further, although the embodiments depicted herein show that theworkpieces 115A and 115B—at the joint—are relatively symmetrical, otherembodiments can have a non-symmetrical configuration. For example, thethickness of the workpiece extension 117A can be thicker or thinner thanthe workpiece extension 117B. Moreover, the workpieces themselves neednot have the same thicknesses or geometry. The joint and workpieces canbe configured so that an acceptable joint is created.

FIG. 4B depicts another exemplary embodiment of the invention, whichallows for easy alignment, where the workpiece 115A has a protrusionportion which mates with a receiving portion P′ on workpiece 115B toallow for the easy alignment of the workpieces. The resultant gaps G andG′ are relatively narrow and can then be welded as described andincorporated herein. Of course, other joint configurations andgeometries can be utilized to allow for ease of alignment. FIG. 4C isanother exemplary embodiment where the protrusion P mates with theprotrusion P′, but the angling of the walls a is different than that ofthe walls b such that contact is made at point P/P′ but gaps G and G′are created to allow for the welding operation. In FIG. 4C theprotrusion portion P and receiving portion P′ represent essentially apoint contact, but in other embodiments, the protrusion P can have othershapes than that shown which allow for alignment and receiving by areceiving portion P′.

In FIG. 1, the laser power supplies 130/230, hot wire power supplies170/270, wire feeder 150/250, and sensing and control unit 195 are shownseparately for clarity. However, in embodiments of the invention thesecomponents can be made integral into a single welding system. Aspects ofthe present invention do not require the individually discussedcomponents above to be maintained as separately physical units or standalone structures.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiments disclosed, but that the invention will includeall embodiments falling within the scope of the appended claims.

1. A system for narrow groove welding, said system comprising: a firstworkpiece that is to be joined to a second workpiece; a laser systemthat comprises at least one laser emitting a laser beam to heat at leastone of said first workpiece and said second workpiece to create at leastone molten puddle; and a wire feeder system comprising at least one wirefeeder feeding at least one wire to said at least one molten puddle,wherein an edge of said first workpiece and an edge of said secondworkpiece are configured such that an alignment of said edge of saidfirst workpiece with said edge of said second workpiece forms a firstgroove and a second groove, wherein said first groove and said secondgroove are formed on opposite sides of said alignment of said firstworkpiece and said second workpiece, wherein said creation of said atleast one molten puddle is in at least one of said first groove and saidsecond groove, wherein for each of said first groove and said secondgroove, a depth is 50% to 75% of a thickness of said first workpiece orsaid second workpiece, a gap width at a surface of said alignment ofsaid first workpiece and said second workpiece is 1.5 to 2 times adiameter of said at least one wire, and a sidewall angle is a range of0.5 to 10 degrees with respect to a centerline of said first groove orsaid second groove, respectively.
 2. The system of claim 1, furthercomprising: at least one power supply to heat said at least one wire toat or near a melting temperature of said at least one wire.
 3. Thesystem of claim 1, wherein said system is configured to weld one grooveat a time.
 4. The system of claim 1, wherein said system is configuredto simultaneously weld said first groove and said second groove.
 5. Thesystem of claim 4, wherein said at least one laser comprises a firstlaser and a second laser to perform said simultaneous welding.
 6. Thesystem of claim 4, wherein said at least one laser comprises one laserand an optical system that directs said laser beam to said first grooveand said second groove to perform said simultaneous welding.
 7. Thesystem of claim 2, wherein a welding of at least one of said firstgroove and said second groove is out-of-position welding, and wherein atleast one of an intensity of said laser beam, a feed speed of said atleast one wire, and a heating of said at least one wire is controlled tominimize sagging of molten metal in said out-of-position weld.
 8. Thesystem of claim 1, wherein said first workpiece self-aligns to saidsecond workpiece in a least one direction when said first workpiece isabutted against said second workpiece.
 9. The system of claim 8, whereinsaid self-alignment comprises alignment of surfaces of said firstworkpiece and said second workpiece after said abutment.
 10. The systemof claim 8, wherein said self-alignment comprises alignment of said gapwidth after said abutment.
 11. A method of narrow groove welding, saidmethod comprising: aligning an edge of a first workpiece to an edge of asecond workpiece; heating at least one of said first workpiece and saidsecond workpiece to create at least one molten puddle; and feeding atleast one wire to said at least one molten puddle, wherein said edge ofsaid first workpiece and said edge of said second workpiece areconfigured such that said aligning forms a first groove and a secondgroove, wherein said first groove and said second groove are formed onopposite sides of said alignment of said first workpiece and said secondworkpiece, wherein said creation of said at least one molten puddle isin at least one of said first groove and said second groove, wherein foreach of said first groove and said second groove, a depth is 50% to 75%of a thickness of said first workpiece or said second workpiece, a gapwidth at a surface of said alignment of said first workpiece and saidsecond workpiece is 1.5 to 2 times a diameter of said at least one wire,and a sidewall angle is a range of 0.5 to 10 degrees with respect to acenterline of said first groove or said second groove, respectively. 12.The method of claim 11, further comprising: heating said at least onewire to at or near a melting temperature of said at least one wire. 13.The method of claim 11, further comprising: welding said second grooveafter welding said first groove.
 14. The method of claim 11, furthercomprising: simultaneously welding said first groove and said secondgroove.
 15. The method of claim 14, wherein said simultaneous welding isperformed using two lasers.
 16. The method of claim 14, wherein saidsaid simultaneous welding is performed using a laser and an opticalsystem that directs a laser beam to said first groove and said secondgroove.
 17. The method of claim 12, further comprising: performingout-of-position welding on at least one of said first groove and saidsecond groove, wherein at least one of an intensity of said heating ofsaid at least one of said first workpiece and said second workpiece, afeed speed of said at least one wire, and a heating of said at least onewire is controlled to minimize sagging of molten metal in saidout-of-position weld.
 18. The method of claim 11, wherein said firstworkpiece self-aligns to said second workpiece in a least one directionwhen said first workpiece is abutted against said second workpiece. 19.The method of claim 18, wherein said self-alignment comprises alignmentof surfaces of said first workpiece and said second workpiece after saidabutment.
 20. The method of claim 18, wherein said self-alignmentcomprises alignment of said gap width after said abutment.